1. Field of the Invention
The invention relates generally to a control apparatus and method for an internal combustion engine, and, more specifically, to a control apparatus and method for an internal combustion engine provided with a throttle valve, an intake valve and an exhaust valve, the control apparatus and method controlling the state in a cylinder when the internal combustion engine is at standstill.
2. Description of the Related Art
Japanese Patent Application Publication No. JP-2005-48718 (JP-A-2005-48718) describes a system that prevents autoignition from occurring when an internal combustion engine is being started. The system determines whether the temperature of a coolant in the internal combustion engine is equal to or higher than a predetermined temperature, when a request to start the internal combustion engine is issued. When it is determined that the temperature of the coolant is equal to or higher than the predetermined temperature, there is a high possibility that autoignition will occur when the internal combustion engine is being started.
In such a case, the system according to the related art initiates starting of the internal combustion engine with the closing timing of an intake valve set to the most delayed closing timing. Then, when an initial combustion is detected, the closing timing of the intake valve is advanced to the regular closing timing. If starting of the internal combustion engine is initiated with the closing timing of the intake valve set to the most delayed closing timing, an increase in the pressure in a combustion chamber during a cranking operation is suppressed. Accordingly, the pressure in the combustion chamber is adjusted so as not to reach the lower limit of the pressure range in which it is highly possible that autoignition occurs when the internal combustion engine is started. As a result, occurrence of autoignition is prevented. Other related arts are described in Japanese Patent Application Publication No. 2005-69049 (JP-A-2005-69049), Japanese Patent Application Publication No. 2002-295288 (JP-A-2002-295288), and Japanese Patent Application Publication No. 2003-262138 (IP-A-2003-262138).
A system that executes a so-called eco-run control for automatically stopping and starting an internal combustion engine has been suggested in order to enhance the fuel efficiency of the internal combustion engine. More specifically, the system that executes the eco-run control automatically stops the operation of the internal combustion engine, when the operating state of the internal combustion engine satisfies a predetermined stop condition. When a predetermined start condition is satisfied after the operation of the internal combustion engine has been stopped, the system automatically starts the operation of the internal combustion engine.
However, when the eco-run control described above is executed, the internal combustion engine may be stopped and started frequently within a short time. Therefore, in many cases, the internal combustion engine is started while the temperature in a cylinder is still high after the internal combustion engine has been stopped. When the temperature in the cylinder is high, autoignition is likely to occur. Occurrence of autoignition may be prevented by executing the control according to the related art described above. In this ease, however, each time the internal combustion engine is started, it is necessary to detect the temperature of a coolant needs, determine whether the temperature of the coolant is equal to or higher than a predetermined temperature, and set the closing timing of an intake valve needs to the most delayed closing timing. However, if the closing timing is at the most delayed closing timing when the internal combustion engine is being started, the startability of the internal combustion engine may be deteriorated because of a decrease in the compression ratio, etc. When the internal combustion engine is automatically stopped and started frequently within a short time, for example, when the eco-run control is executed, it is desirable to execute a control under which the internal combustion engine is started with higher startability.